The aim of this project is to investigate the transport of liposome entrapped substances into the skin and to the inner layers of the skin, by EPR in vivo and to approach the actual conditions which are used in local application of liposomes on humans. These experiments will contribute to the optimization of liposomal formulations for topical application on humans in dermatology, in skin care, and in protection of the skin by liposomes. For this purpose different nitroxides will be entrapped in the liposomes and the EPR spectra intensity decay will be measured with time after application of liposomes on skin or after intradermal injection of liposomes. The intensity decay is a consequence of liposome disintegration, reduction of nitroxides on the skin or inside the skin, and clearance of nitroxide by blood flow. We postulate that with in vivo EPR information can be obtained about the stability of liposomes in contact with skin and about their transport into the skin and within the skin.